Unusual echinoid resting trace records change in the position of the redox boundary (Palaeogene of the Lesser Caucasus in Georgia)
Authors
Alfred Uchman
Faculty of Geography and Geology, Institute of Geological Sciences, Jagiellonian University, Gronostajowa 3a, 30-387 Kraków
Zurab Lebanidze
Department of Geology, Faculty of Exact and Natural Sciences, Iv. Javakhishvili Tbilisi State University, University str. 13, 0186 Tbilisi
Nino Kobakhidze
Alexander Janelidze Institute of Geology, Iv. Javakhishvili Tbilisi State University, Politkovskaia 31, 0186 Tbilisi
Tamar Beridze
Alexander Janelidze Institute of Geology, Iv. Javakhishvili Tbilisi State University, Politkovskaia 31, 0186 Tbilisi
Davit Makadze
Alexander Tvalchrelidze Caucasian Institute of Mineral Resources, Tbilisi State University, 12 Mindeli str., 0186 Tbilisi
Koba Lobzhanidze
Alexander Janelidze Institute of Geology, Iv. Javakhishvili Tbilisi State University, Politkovskaia 31, 0186 Tbilisi
Sophio Kutsishvili
Alexander Janelidze Institute of Geology, Iv. Javakhishvili Tbilisi State University, Politkovskaia 31, 0186 Tbilisi
Rusudan Chagelishvili
Department of Geology and Paleontology, Georgian National Museum, 3 Purtseladze str., 0105 Tbilisi
Kakha Koiava
Department of Geology, Faculty of Exact and Natural Sciences, Iv. Javakhishvili Tbilisi State University, University str. 13, 0186 Tbilisi
Nino Khundadze
Alexander Tvalchrelidze Caucasian Institute of Mineral Resources, Tbilisi State University, 12 Mindeli str., 0186 Tbilisi
Keywords:
Ichnotaxonomy, New ichnotaxa, Irregular echinoids, Deep sea, Flysch, Redox boundary, Oxygenation
Abstract
The first recognition of a tracemaker responding to a temporary shift in the redox boundary is recognized. This is recorded by a new trace fossil, Sursumichnus orbicularis igen. et isp. nov., which is established for mound-like structures on the upper surfaces of sandstone beds from the Borjomi Flysch (upper Paleocene–lower Eocene) in the Lesser Caucasus (Georgia). It is connected with the spatangoid echinoid burrow Scolicia de Quatrefages, 1849 and interpreted as a resting trace of the same tracemaker produced after moving up from a deeper position within the sediment. The resting is caused by an episode of unfavourable conditions related to shallowing of the redox boundary. The trace fossil is a component of the Nereites ichnofacies.
